The present invention is directed to new polymeric biguanides having potent antimicrobial activity and little, if any, toxicity relative to human tissues. The amidopolybiguanides disclosed herein have many industrial applications, but are especially useful as antimicrobial preservatives in pharmaceutical compositions. The invention is particularly directed to the use of these compounds in compositions and methods for disinfecting contact lenses, and to the preservation of various types of ophthalmic and otic pharmaceutical compositions.
Contact lenses are exposed to a broad spectrum of microbes during normal wear and become soiled relatively quickly. Routine cleaning and disinfecting of the lenses are therefore required. Although the frequency of cleaning and disinfecting may vary somewhat among different types of lenses and lens care regiments, daily cleaning and disinfecting is normally required. Failure to clean and disinfect the lens properly can lead to a multitude of problems ranging from mere discomfort when the lenses are being worn to serious ocular infections. Ocular infections caused by particularly virulent microbes, such as Pseudomonas aeruginosa, can lead to loss of the infected eye(s) if left untreated, or if allowed to reach an advanced stage before treatment is initiated. It is therefore extremely important that patients disinfect their contact lenses in accordance with the regimen prescribed by their optometrist or ophthalmologist.
Unfortunately, patients frequently fail to follow the prescribed regimens. Many patients find regimens to be difficult to understand and/or complicated, and as a result do not comply with one or more aspects of the regimen. Other patients may have a negative experience with the regimen, such as ocular discomfort attributable to the disinfecting agent, and as a result do not routinely disinfect their lenses or otherwise stray from the prescribed regimen. In either case, the risk of ocular infections is exacerbated.
Despite the availability of various types of contact lens disinfecting systems, such as heat, hydrogen peroxide, and other chemical agents, there continues to be a need for improved systems which: 1) are simple to use, 2) have potent antimicrobial activity, and 3) are nontoxic (i.e., do not cause ocular irritation as the result of binding to the lens material). Conventional contact lens cleaners with potent antimicrobial activity also have rather high toxicity. There is, therefore, a particular need in the fields of contact lens disinfection and ophthalmic composition preservation for safe and effective chemical agents with high antimicrobial activity and low toxicity.
The use of polymeric biguanide compounds as disinfecting agents is well known. Commercially available polybiguanides are hexamethylene biguanide polymers that have end groups consisting of a cyanoguanidine group and an amino group, respectively. The widely-used polybiguanide Cosmocil CQ (polyhexamethylene biguanide or xe2x80x9cPHMBxe2x80x9d) has strong antimicrobial activity, but rather high toxicity. A principal objective of the present invention is to provide polymeric biguanides that preserve antimicrobial activity comparable to PHMB, but are less toxic to human tissue than PHMB. As explained below, this objective has been achieved by means of a unique modification of the terminal amino groups of PHMB.
The present invention is directed to satisfaction of the above-cited needs and objectives.
The present invention is directed to polybiguanides having an amido moiety as the first terminal group and a cyanoguanidine moiety as the second terminal group. These compounds have antimicrobial activity comparable to PHMB, but are generally less toxic than PHMB. The invention is also directed to contact lens disinfecting compositions which contain the subject compounds, and to various ophthalmic compositions (e.g., pharmaceuticals, artificial tears, and comfort drops) and other types of pharmaceutical compositions that contain the compounds for purposes of preserving the compositions against microbial contamination.
The modification of the amino moiety of known polybiguanides to an amido moiety containing the substituents described herein results in good antimicrobial activity and lowered toxicity over prior art compounds. Also, the addition of specified substituents to the PHMB polymer changes its physicochemical and biochemical properties to afford a compound whose toxicity profile is lower than that of PHMB, yet maintains the antimicrobial activity of PHMB.
As discussed above, Cosmocil CQ is a widely-used, commercially available polyhexamethylene biguanide (xe2x80x9cPHMBxe2x80x9d) disinfectant containing one terminal amino group. PHMB has strong antimicrobial activity, but rather high toxicity. A key difference between the compounds of the present invention and conventional PHMB is the modification of the terminal amino group of PHMB to form an amido group. This modification has resulted in the production of a new class of compounds having properties that are superior to those of PHMB. This invention also involves a modification of the PHMB polymer to include other substituents that change its physical, chemical, and biochemical properties to provide compounds whose toxicity profiles are lower than that of PHMB, while still maintaining the potent antimicrobial activity of PHMB.
The compounds of the present invention are polybiguanides in which the first terminal group is an amido moiety and the second terminal group is a cyanoguanidine moiety. The compounds have the following formula:
RC(xe2x95x90O)NHxe2x80x94Xxe2x80x94[NHC(xe2x95x90NH)NHC(xe2x95x90NH)NHxe2x80x94Xxe2x80x94]nNHC(xe2x95x90NH)NHCNxe2x80x83xe2x80x83(I)
wherein:
n is a whole number in the range of 1 to 100;
X is saturated or unsaturated alkyl, cycloalkyl, alkyl substituted with cycloalkyl, aryl, or aralkyl, with the proviso that the X groups contain 1 to 40 carbon atoms (C1 to C40) and are unsubstituted or substituted with any number of N, O, S, P, B, F, Cl, Br, or I; and
R is a saturated or unsaturated alkyl (C1 to C50), cycloalkyl (C3 to C50), alkyl substituted with cycloalkyl, polyethylene oxide having a molecular weight of 50 to 10,000 (M.W. 50-10,000), polypropylene oxide having a molecular weight of 50 to 10,000 (M.W. 50-10,000), any combination of the above groups, unsubstituted aralkyl, aralkyl substituted with any number of N, O, S, P, B, F, Cl, Br, or I unsubstituted aryl, or aryl substituted with any number of N, O, S, P, B, F, Cl, Br, or I.
The R substituent in compounds of formula (I) optionally include amide, urea or other covalent linking functional groups.
As utilized herein, the term xe2x80x9calkylxe2x80x9d includes straight or branched chain hydrocarbon groups. The alkyl groups may be substituted with other groups, such as halogen, hydroxyl or alkoxyl.
The preferred compounds are those wherein n is 4 to 16, X is alkyl or aralkyl, and R is polyethylene oxide (M.W. 100 to 2,000) or polyethylene oxide (M.W. 100 to 2,000) alkyl ether. The use of polyethylene oxide as the R group is preferred because this substituent has been found to be particularly effective in reducing the toxicity of biguanides. The following compounds are particularly preferred:
Compound Number 2 above is the most preferred.
The compounds of the present invention may be prepared by means of the method illustrated in Scheme 1 below: 
In general, the synthesis of the amido biguanides of the present invention is performed by reaction of the terminal amino group of a polybiguanide with an N-hydroxysuccinimide ester of the desired substituent, R, in the presence of a sterically hindered base, preferably diisopropylethylamine, in a suitable solvent, preferrably DMSO, at ambient temperature for 8-20 hours.
The compounds of the present invention wherein R is a polyethylene oxide may be prepared by the means of the method illustrated in Scheme 2 below: 
Synthesis of Compound 5
A 50 ml chloroform solution of 11.0 g (0.02 mol) poly(ethyleneglycol) (polyethyleneoxide, PEO) MW 550 monomethylether (Aldrich lot# 05022ET) and 1.6 g (0.02 mol) pyridine was added dropwise under an N2 atmosphere to a 75 ml chloroform solution of 3.09 g (0.026 mol) thionyl chloride. After addition, the reaction mixture was heated to reflux (70xc2x0 C.) under constant stirring for 2.5 hours. The organic layer was washed with 3xc3x9750 ml aqueous sodium chloride and sodium carbonate followed by 2xc3x9760 ml aqueous sodium chloride, dried (sodium sulfate), filtered and concentrated in vacuo to obtain 11.14 g (0.0196 mol, 98.0%) of Compound 5. The structure was confirmed with NMR by observing the change in chemical shift from a methylene adjacent to the terminal hydroxyl group (xcex43.69, t, 2H) to a methylene adjacent to the terminal chloro group (xcex43.77, t, 2H).
Synthesis of Compound 6
2.85 g (0.005 mol) of Compound 5 and 1.21 g (0.0065 mol) potassium phthalimide were mixed in 10 ml dimethylformamide (DMF) and heated to 120xc2x0 C. under constant stirring for 4 hours. The DMF was removed in vacuo and the remaining residue was dissolved in 20 ml chloroform, filtered and concentrated in vacuo to yield 3.4 g (0.005 mol, 100%) of Compound 6. The structure was confirmed with NMR by observing the appearance of aromatic phthalimide peaks (xcex47.70 and 7.85, m, 4H) and change in chemical shift from a methylene adjacent to the terminal chloro group (xcex43.77, t, 2H) to a methylene adjacent to the terminal phthalimide group (xcex43.90, t, 2H).
Synthesis of Compound 7
3.4 g (0.005 mol) of Compound 6 and 5 g (0.011 mol) hydrazine (35% w/w in water) were dissolved in 130 ml ethanol and heated to reflux (80xc2x0 C.) overnight. The solution produced copious precipitation which was filtered after heating. The residue was dissolved in ethyl acetate and refrigerated overnight to induce precipitation of phthalhydrazide. The solution was filtered and redissolved in chloroform and refrigerated overnight. The solution was then filtered and concentrated in vacuo to yield 2.08 g (0.0038 mol, 75.6%) of Compound 7. The structure was confirmed with NMR by observing the dissappearance of phthalimide peaks and appearance of a methylene adjacent to the terminal primary amine group (xcex42.86, t, 2H).
Synthesis of Compound 8
7.75 g (0.014 mol) of Compound 7, 1.75 g (0.0175 mol) succinic anhydride and 2.59 g (0.02 mol) N,N-diisopropylethylamine were dissolved in 100 ml chloroform and heated to reflux (70xc2x0 C.) for four hours. The reaction mixture was then diluted to 150 ml and washed with 3xc3x9750 ml aqueous sodium chloride and 1N HCl followed by 2xc3x9750 ml aqueous sodium chloride. The solution was then dried (sodium sulfate), filtered and concentrated in vacuo to yield 7.11 g (0.011 mol, 78.2%) Compound 8. The structure was confirmed with NMR by observing the appearance of succinyl methylene groups (xcex42.55 and 2.65, m, 4H) and change in chemical shift from a methylene adjacent to an amine (xcex42.86, t, 2H) to a methylene adjacent to an amide (xcex43.44, t, 2H).
Synthesis of Compound 4
2.85 g (0.0044 mol) of Compound 8 and 0.51 g (0.0044 mol) N-hydroxysuccinimide were dissolved in 40 ml tetrahydrofuran and stirred for 20 minutes. Then 0.91 g (0.0044 mol) 1,3-dicyclohexylcarbodiimide (DCC) were added and the reaction mixture stirred overnight. 8 drops of glacial acetic acid were added to convert the remaining DCC into DCU (dicyclohexylurea). This was monitored by IR observing the disappearance of the diimide peak (2100 cmxe2x88x921). The mixture was then concentrated in vacuo, dissolved in ethyl acetate (40 ml) and refrigerated to induce crystallization of DCU. The solution was then filtered and concentrated in vacuo to yield 3.28 g (0.0044 mol, 100%) of PEO MW 550 succinimidyl succinamide monomethyl ether. The product was confirmed with NMR by observing the appearance of the N-hydroxysuccinimide methylene groups (xcex42.84, s, 4H) and change in chemical shift from succinyl methylene groups (xcex42.55 and 2.65, m, 4H) to succinimidyl succinamide methylene groups (xcex42.99 and 2.61, t, 4H).
The compounds of the present invention display a strong antimicrobial activity profile, as discussed above, which is similar to unmodified polyhexamethylene biguanide (xe2x80x9cPHMBxe2x80x9d), but exhibit significantly lower toxicity than the unmodified PHMB.
The compounds discussed herein can be used individually or in combination with other disinfectants or preservatives. The amount of each compound used will depend on the purpose of the use, e.g., disinfection of contact lenses or preservation of pharmaceutical products, and the absence or inclusion of other antimicrobial agents. The concentration determined to be necessary for the above-stated purposes can be functionally described as xe2x80x9can amount effective to disinfectxe2x80x9d and xe2x80x9can amount effective to preserve,xe2x80x9d or xe2x80x9cmicrobicidally effective amounts,xe2x80x9d or variations thereof. The concentrations used for disinfection will generally be in the range of from about 0.00001 to about 0.01% by weight based on the total weight of the composition (xe2x80x9cwt. %xe2x80x9d). The concentrations used for preservation will generally be in the range of from about 0.00001 to about 0.001 wt. %.
The compositions of the present inventions may be aqueous or nonaqueous, but will generally be aqueous. As will be appreciated by those skilled in the art, the compositions may contain a wide variety of ingredients, such as tonicity agents (e.g., sodium chloride or mannitol), surfactants (e.g., polyvinyl pyrrolidone and polyoxyethylene/polyoxypropylene copolymers), viscosity adjusting agents (e.g., hydroxypropyl methyl cellulose and other cellulose derivatives) and buffering agents (e.g., borates, citrates, phosphates, and carbonates). The ability of the compounds of the present invention to retain their antimicrobial activity in the presence of such agents is a significant advantage of the present invention.
The pharmaceutical compositions of the present invention will be formulated so as to be compatible with the human tissues to be treated with the compositions (e.g., tissues of the eye or ear), or the contact lenses to be treated. Formulations that meet these basic requirements are referred to herein as xe2x80x9cpharmaceutically acceptable vehiclesxe2x80x9d for the compounds of the present invention or, in the case of compositions for treating the eye or contact lenses, xe2x80x9cophthalmically acceptable vehiclesxe2x80x9d.
As will be appreciated by those skilled in the art, the ophthalmic compositions intended for direct application to the eye will be formulated so as to have a pH and tonicity which are compatible with the eye. This will normally require a buffer to maintain the pH of the composition at or near physiologic pH (i.e., 7.4) and may require a tonicity agent to bring the osmolality of the composition to a level at or near 280 to 320 milliosmoles per kilogram of water (xe2x80x9cmOsm/kgxe2x80x9d). The formulation of compositions for disinfecting and/or cleaning contact lenses will involve similar considerations as well as considerations relating to the physical effect of the compositions on contact lens materials and the potential for binding or absorption of the components of the composition by the lens.
The contact lens disinfecting compositions of the present invention will preferably be formulated as aqueous solutions, but may also be formulated as nonaqueous solutions as well as suspensions, gels, and so on. The compositions may contain a variety of tonicity agents, surfactants, viscosity adjusting agents, and buffering agents, as described above.
The above-described compositions may be used to disinfect contact lenses in accordance with processes known to those skilled in the art. More specifically, the lenses will first be removed from the eyes of the patients, and then will be immersed in the compositions for a time sufficient to disinfect the lenses. This immersion will typically be accomplished by means of soaking the lenses in a solution overnight (i.e., approximately six to eight hours). The lenses will then be rinsed and placed in the eye. Prior to immersion in the disinfecting compositions, the lenses will preferably also be cleaned and rinsed.
The compositions and methods of the present invention may be used in conjunction with various types of contact lenses, including both lenses generally classified as xe2x80x9chardxe2x80x9d and lenses generally classified as xe2x80x9csoft.xe2x80x9d
The compounds of the present invention may also be included in various types of pharmaceutical compositions as preservatives, so as to prevent microbial contamination of the compositions. The types of compositions which may be preserved by the compounds of the present invention include: ophthalmic pharmaceutical compositions, such as topical compositions used in the treatment of glaucoma, infections, allergies, or inflammation; otic pharmaceutical compositions, such as topical compositions instilled in the ear for treatment of inflammation or infection; compositions for treating contact lenses, such as disinfecting solutions, cleaning products and products for enhancing the ocular comfort of patients wearing contact lenses; other types of ophthalmic compositions, such as ocular lubricating products, artificial tears, astringents, and so on; dermatological compositions, such as anti-inflammatory compositions, as well as shampoos and other cosmetic compositions; and various other types of pharmaceutical compositions. The present invention is not limited with respect to the types of pharmaceutical compositions in which the compounds of the present invention may be utilized as preservatives.
The following examples are presented to further illustrate various aspects of the present invention.